Afterburner flameholder construction

ABSTRACT

An afterburner on a turbofan engine includes a flameholder means having an annular flameholder gutter positioned downstream of a first exhaust means of a core engine while said flameholder means also includes a plurality of radial gutter sections extending radially outward towards an outer wall of said afterburner and downstream of a second annular exhaust means of a bypass duct around said core engine; a plurality of said radial gutter sections having a manifold extending along the forward portion thereof, each manifold having an inlet at its inward end located downstream of said first exhaust means with said manifold directing a hot exhaust flow from said inlet to openings on each side of its associated radial gutter section in a portion downstream of said second annular exhaust means.

The Government has rights in this invention pursuant to Contract No.F33657-76-C-0408 awarded by the Department of the Air Force.

BACKGROUND OF THE INVENTION

This invention relates to the use of flameholders with afterburnershaving an annular bypass air exit into an afterburner around exhaustflow from a core engine. The patents to Nelson, U.S. Pat. No. 3,295,325and to Riecke, U.S. Pat. No. 3,485,045, show afterburners for bypassengines having flameholder constructions. Nelson uses a specific shapeof a flame stabilizing ring to force hot air or flame outwardly andRiecke uses scoops on his annular flameholder to cause a positivetransfer of flame outwardly. The patent to Marshall et al, U.S. Pat. No.3,800,527, shows a heat shield for preheating a flameholder. The patentsto Pierce, U.S. Pat. No. 2,978,865 and to Coplin et al, U.S. Pat. No.3,330,117, and to Kohler et al, U.S. Pat. No. 3,595,024, provide meansfor mixing bypass air and core engine air.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide for flamestability during afterburning in the afterburner of a turbofan engine.

In accordance with the present invention, a flameholder includes anannular gutter-type flameholder having a plurality of radially extendinggutter-type extensions. Said annular gutter-type flameholder beinglocated rearwardly from the exhaust of said core engine with some radialflameholder sections extending inwardly and some extending outwardlyinto the exhaust of the fan air. A plurality of said outwardly extendingradial flameholders having a manifold formed around the forward partthereof along its entire length with an inlet scoop in line with gasesexiting from said core engine. Said manifold carrying the heated exhaustair from said core engine to the outer portion of said radialflameholder where it is directed rearwardly from each side thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a portion of the turbofan engine broken away showingthe core engine exhaust and fan exhaust entering into an afterburnerwith the flameholder shown partially in section;

FIG. 2 is an enlarged view of a portion of the flameholder as it isviewed from the front thereof in FIG. 1;

FIG. 3 is an enlarged view taken on the line 3--3 of FIG. 2; and

FIG. 4 is an enlarged view taken on the line 4--4 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, we see the outer engine case 12 of a turbofanengine, such as shown in U.S. Pat. No. 3,295,325. The turbofan enginedirects fan flow through annular bypass air passage 30 where it isdischarged into afterburner section 26. Exhaust from the core engine isdischarged through annular gas passage 38 in afterburner section 26. Areheat process takes place in afterburner section 26 and this requiresthe injection of additional fuel in the afterburner section 26 and theestablishment of a flow stabilization zone in the afterburner section 26so that combustion may take place therein. Flameholder 50 performs theflame stabilization zone creating function.

Referring to FIG. 1, we see flameholder 50 and its support mechanism ingreater particularity. Flameholder 50 is supported between the enginecenter body 40 and outer case 12 in a manner to be hereinafterdescribed. The afterburner section 26 is formed having a cooling liner 6spaced inwardly from the outer case 12. The forward end of the liner 6is located as far forward as possible to have only the cooler outer airdirected therethrough.

A fuel system including a fuel control 8 delivers a scheduled fuelsupply to five fuel injection zones, I, II, III, IV and V. As theafterburner is ignited, fuel is directed to Zone I. As the power leveris advanced, fuel is also directed to Zone II, then to Zone III and thento Zone IV. Zone IV comprises a set of three radially spacedconventional sprayrings 66, 68 and 70. Fuel is then directed to Zone V.

Flameholder 50 is formed having a pair of spaced annular walls 14 and16. While the rearward portions of the walls 14 and 16 are spacedapproximately parallel, the forward portions taper inwardly toward eachother and are fixed together by a plurality of spaced support plates 20.The plates 20 extend into the area between the walls 14 and 16 andsupport an annular flameholder gutter 22 therein. The forward end of thewall 14 is straight but the forward end of the wall 16 is curved, as at24. The opening between the forward end of wall 14 and the curvedforward end 24 of the wall 16 is positioned axially in line with theexhaust opening from the core engine; therefore, exhaust gases flowingfrom the core engine are directed over the flameholder gutter 22. As isshown in prior art patents set forth above, radially extendingflameholder gutter sections 32 extend inwardly from wall 14 and radiallyextending gutter sections 34 extend outwardly from wall 16. These radialflameholder gutter sections 32 and 34 are welded to their respectivewalls 14 and 16 with the respective wall cut out within the gutter endso that the flame can extend from within walls 14 and 16 through theradial gutter sections.

Twenty-four equally spaced radial gutter sections 34 extend outwardlyand eight equally spaced radial gutter sections 32 extend inwardly. Theradial gutter sections 32 and 34 were spaced so that one gutter section32 lined up with one gutter section 34. The inner end of each guttersection 32 where it is welded to wall 14 is also supported by a plate 36which is welded to each gutter section 32 and plate 14. Further theinner end of each gutter section 32 is formed having flanges 38extending to each side thereof. Adjacent flanges 38 of gutter sections32 are connected together by a plate member 41. This provides forrigidity in the construction of the flameholder 50.

A plurality of the support plates 20 around the flameholder 50 extendforwardly and additional amount so that the support end of an attachingrod 42 can be fixed thereto, (see FIG. 1) such as by bolting. Theforward end of each of the rods 42 is attached by a bracket 44 fixed atspaced points around the inner side of engine case 12. These rods 42position and support the flameholder 50.

The eight radial gutter sections 34 which are aligned with the eightradial gutter sections 32, have the support plates 20 extending over thecurved end 24 and along the outer surface of wall 16 and extendingoutwardly along the center of the gutter sections 34 for added rigidity.These gutter sections 34 are wider than the gutter sections which arenot aligned. This can be seen at A in FIG. 2. The support plates 20 arewelded in place.

Each of the two outwardly extending radial gutter sections 34, locatedbetween the radial gutter sections 34 aligned with the radial guttersections 32, are formed with a manifold 55 welded in position aroundeach radial gutter section 34.

Each manifold 55 has a forwardly extending inlet 57 which is welded inposition to the outer surface of wall 16. The forwardly extending inlets57 are positioned axially in line with the exhaust opening from the coreengine so that exhaust gases flowing from the core engine can bedirected into each opening 57 and through each associated manifold 55.Manifold 55 has its rearward edges welded to its cooperating radialgutter section 34 outwardly to point B (see FIG. 3); at that point, theend of manifold 55 is spaced from the rear end of the radial guttersection 34 forming two axial openings 61 and 62 for the outer portion ofthe radial gutter section 34. It can be seen that hot exhaust gases fromthe core engine will be delivered through the inlet 57 and the manifold55 to the openings 61 and 62 on each side of the associated radialgutter section 34. In one construction built, the inlets 57 were sizedto receive 1% of the hot exhaust gases passing from the core engine.

We claim:
 1. In combination, a core engine, a bypass duct around saidengine, said core engine having a first exhaust means discharging a hotexhaust, said bypass duct having a second annular exhaust meansdirecting a cooler flow therefrom, said first and second exhaust meansopening directly into an afterburner, said afterburner having an outerwall extending downstream from said bypass duct, a flameholder means insaid afterburner downstream of said first and second exhaust means, saidflameholder means having an annular gutter section positioned downstreamof said first exhaust means in said hot exhaust, a plurality of radialgutter sections extending radially outward from said flameholder meansthrough said hot exhaust of said first exhaust means and into saidcooler flow of said second exhaust means towards said outer wall of saidafterburner downstream of said second exhaust means, a plurality of saidradial gutter sections having a manifold on the forward portion thereof,each manifold having an inlet opening located downstream of and in linewith said first exhaust means, each manifold having outlet openings oneach side of said radial gutter section and in a portion downstream ofand in line with said second annular exhaust means, said manifolddirecting hot exhaust flow from its inlet opening to its outletopenings.
 2. A combination as set forth in claim 1 wherein each manifolddirects a hot exhaust flow from said inlet opening located between themanifold and radial gutter section to outlet openings formed betweensaid manifold and the cooperating radial gutter section.
 3. Acombination as set forth in claim 1 wherein the outlet openings are onlylocated at the outer radial portion of the radial gutter section.
 4. Acombination as set forth in claim 1 wherein said outlet openings areelongated in a radial direction.
 5. A combination as set forth in claim1 wherein each manifold covers the forward portion of its cooperatingradial gutter section.